Compliant structural members

ABSTRACT

Lightweight, porous, compliant structural members comprising an assemblage of metallic strips disposed in side-by-side relationship with the edges of the strips at opposite sides of the assemblage. There are interstices between the strips, and the edges of the strips are fixed relative to each other on at least one side of the assemblage to maintain the strips in the proper relationship.

This is a division of application Ser. No. 335,320 filed Feb. 23, 1973now U.S. Pat. No. 3,916,054.

This invention relates to novel, improved, lightweight, porous, strong,stable, durable members which are useful for a variety of purposes whichwill be readily apparent from the disclosure herein and in theaccompanying drawing to those persons skilled in the arts to which theinvention relates.

At the present time turbine and compressor rub rings and labyrinth sealsare particularly important uses to which the novel members of thepresent invention may be put. The principles of the invention and itsfeatures and advantages will be developed primarily by reference tothese particular applications of it. It is to be understood, however,that this is for the sake of clarity and the reader's convenience and isnot intended to limit the scope of the invention.

In both the compressor and turbine sections of turbine engines and inother machines as well, a rotor (or wheel or fan) consisting of acentral shaft carrying one or more rows of radially extending bladesrotates in a cooperating, stationary housing or shroud surrounding therotor. Typically, the rotor reaches an elevated temperature duringoperation; and a considerable clearance must be left between the bladetips and the housing or shroud to accommodate differential expansionbetween the rotating and stationary components of the machine.

If sufficient clearance to accommodate thermal expansion is provided,the air or other gas in the housing can be pumped past the tips of therotor blades in significant quantities, substantially reducing theefficiency of the machine.

Accordingly, a number schemes for preventing gas flow between the tipsof the rotor blades and the stationary structure in which the rotorrevolves during operation of the machine have been proposed.

One of the first proposals involved the use of squealers on the rotorblades to produce a rubbing type seal with a limited area of contactbetween the blade tips and the surrounding stationary structure (asquealer is a blade tip thinned to rub against the surrounding structureand provide a seal with a minimum of heating). Squealers have obviousdrawbacks and were replaced by seals fabricated from open-facedhoneycomb type materials. Examples of such seals are disclosed in U.S.Pat. Nos. 2,963,307 issued Dec. 6, 1960 to Bobo for HONEYCOMB SEAL and3,056,853 issued Oct. 2, 1962 to Varadi for RETAINING MEANS FOR TURBINESHROUDS AND NOZZLE DIAPHRAGMS OF TURBINE ENGINES.

While an improvement on squealers, honeycomb seals also proved to have anumber of disadvantages. Honeycomb materials with small cell sizes areexpensive. Also, such honeycomb structures are relatively stiff.Stiffness, coupled with the relatively large area of contact whichoccurs when small cell sizes are employed, produces considerablefriction between the blade tips and the seal. The result is excessivewear of the blade tips and detrimental overheating of the seal.

If large cell sizes are used in order to reduce the contact area andeliminate excessive friction, the cell sizes become so large that axialflow or pumping of the gases across the rotor blade tips occurs; andthis is the very phenomenom which is to be eliminated, attenuated oravoided, if possible. Also, disadvantages common to all honeycomb typeseals such as high cost, stiffness, and difficulty in forming the stripsfrom which the honeycomb structure is made remain.

An even less satisfactory arrangement than that of the honeycomb typefrom the point-of-view of rubbing friction, high cost, inability toprevent axial flow, and other of the drawbacks discussed above, would bethe unitary, grid-type material described in U.S. Pat. No. 3,042,365issued July 3, 1962 to Curtis for BLADE SHROUDING.

To take advantage of the reduction in rubbing friction which can beobtained by employing larger cell sizes and yet avoid flow past theblade tips, it has been proposed that the cells of honeycomb seals befilled with an abradable, heat resistant material. Exemplary seals ofthis character are described in U.S. Pat. Nos. 3,053,694 issued Sept.11, 1962 to Daunt for ABRADABLE MATERIAL: 3,068,016 issued Dec. 11,1962to Dega for HIGH TEMPERATURE SEAL: and 3,126,149 issued Mar. 24, 1964 toBowers for FOAMED ALUMINUM HONEYCOMB ROTOR RUB-IN SHROUD. Although axialgas flow past the rotor tips is reduced in filled honeycomb materials,the other disadvantages of honeycomb type seals, some of which arediscussed above, are not eliminated. In addition, difficulties can beexperienced in retaining the filler material in the honeycomb matrix.

A seal of a "filled" material which would be inferior to that of thetype just described in disclosed in U.S. Pat. No. 3,092,306 issued June4, 1963 to Eder for ABRADABLE PROTECTIVE COATING FOR COMPRESSOR CASINGS.The Eder coating would be even stiffer than the honeycomb structure andwould have a greater area of rubbing contact. It would be expensive toinstall and to replace and would have other drawbacks as well.

Another type of heretofore developed sealing arrangement forapplications of the type in question is made of felted metal fibers ofmetal fibers sintered into a mat. Like those of honeycomb typeconstruction, seals of this type have a number of disadvantages. Thefibers used for this purpose have small diameters and, consequently,large surface area. They are therefore highly susceptible to oxidationand, indeed, suitable only for applications wherein the temperature doesnot exceed about 1200° F., even when the most oxidation resistantmaterials are employed, as oxidation rates become catastrophic at highertemperatures.

Furthermore, such material is not self-supporting and must accordinglybe attached to a backing member or support. In the process of welding orbrazing the felted material to the backing member, the brazing alloy orweld metal typically fills the interstices between the fibers by virtureof capillary flow. This significantly degrades the compliance andabradable characteristics of the material, characteristics which arehighly desirable for the uses described herein.

Also, seals of this character generally have low strength. Further, theyalso lack the durability needed to withstand periodic engine cleaning.

Still another type of seal for minimizing axial leakage in turbines andthe like is disclosed in U.S. Pat. No. 3,092,393 issued June 4, 1963, toMorley for LABYRINTH SEALS. The Morley seals consists of a stack orseries of annular metal strips which are attached to the stationarycomponent of the machine in which the seal is installed and are spacedapart at the surface of the assemblage where contacted by the associatedrotating component of the machine. The annular members ae made of amaterial which is softer or has a lower melting point than the rotatingcomponent of the machine in which the seal is installed so that theywill wear away where contacted by the rotating component.

The Morley seal is nothing more than a modification or extension of aconventional labyrinth seal and would have much the same disadvantagesof the latter. Specifically, because of its construction, the stripsforming the Morley seal would have to be relatively stiff andnon-resilient. As a result, they would be expected to have a low degreeof compliance and would not be capable of maintaining an effective seal,particularly in circumstances involving significant temperature changesor temperature differentials which produce expansion and contraction ofthe metal structures accompanying such thermal changes. In addition, theMorley structures would not be effective seals because of the largespaces between the strips and, in this regard, would be less efficientthan honeycomb seals which, as discussed above, have not proven totallysatisfactory as they are required to be modified as by filling the poreswith an abradable material.

We have now developed a novel, lightweight, porous, durable, stablematerial which can be employed to make seals that are free of thedisadvantages of those discussed above and which provide superiorsealing for compressors, turbines, and similar machines in addition tostructures which are useful for many other purposes.

In brief, our novel structures or materials consist of an assemblage ofmetallic foils or strips disposed in side-by-side relationship with theedges of the foils at opposite sides of the assemblage and with theedges of the strips at one side of the assemblage bonded together orotherwise fixed relative to each other. This may and typically will beaccomplished by bonding a support or backing member to the edges of thestrips on one side of the assemblage.

Part or all of the strips are corrugated or otherwise embossed. Thecorrugations are formed and the adjacent strips positioned in such amanner as to prevent nesting and to create interstices between thestrips while limiting the pore area at the surface of the structuredefined by the exposed edges of the corrugated strips. It has beenfound, for example, that surfaces which are 70-95% sealed and which havepore sizes as small as 0.0005 to 0.010 inch can readily be obtained.

"Nesting" is used herein to identify the condition in which one stripcontacts an adjacent strip or strips over a substantial area and therebyeliminates interstices between the strips to a significant extent.Nesting can also be avoided by using felted, knitted, or similarmaterials between the strips, if desired.

Also, because of the pore configuration, the novel structures we haveinvented keep the bonding metal in its liquid state from flowing bymeans of capillary action or "wicking" through the assemblage of stripswhen the support or backing member is attached. This eliminates theadverse changes in abradability attributable to the presence of therelatively solid-surfaced bonding metals as well as the accompanying,unwelcome increase in the thermal conductivity of the structure.

Due primarily to the unique interstitial configurations which can beprovided, structures formed in accord with the principles of the presentinvention also afford superior components of the filled type because ofthe tenacity with which the filler material is retained in place by thecorrugated or embossed metal foil strips.

Also, again because of the unique interstitial arrangements, essentiallyall convective gas flows in the foil assemblages of our novel structuresare eliminated. As a result, in high temperature applications thestructures of the present invention as well as the components in whichthey are mounted remain cooler than when prior art assemblages such asthose described above are employed.

In addition to having limited pore areas, the novel structures describedhereinbefore are self-supporting. Further, they possess a high degree ofcompliance in applications where they are rubbed by rotor blade tips andribbed structures. For example, they will readily adjust to a zerotolerance fit with the contacting surface of the blade or otherrelatively movable member by abrading, folding, bending, smearing,fraying, and/or by elastic displacement and compression of the foils.Because of their high compliance, the novel structures of the presentinvention will also accommodate a considerable amount of misalignmentbetween the components spanned by them. At the same time, they do notexhibit significant anti-clastic effects; that is, they can be bent orcurved in one direction without incurring damaging distortion indirections normal to the bend.

A related advantage is that the compliance of our novel structuresremains high even in applications where changing temperatures ortemperature differentials cause thermal expansion and/or contraction ofthe metallic assemblage which induces changes in the distances betweenthe components sealed by the structure.

To minimize friction, anti-gall or friction treatments may be applied tothe working surfaces of the structures of the present invention and/orto the surfaces of the components which rub against them. Suitabletreatments include nitriding, boriding, cyaniding and coating or surfaceimpregnation with materials such as molybdenum disilicide, graphite,Teflon, and aluminum oxide.

Another advantage of our invention is that a wide range of our inventionis that a wide range of abradability and/or compliance or elasticity anda porosity which ranges from almost zero up to a level sufficiently highto allow pumping to occur, or higher, can be provided by varying theconfiguration and/or the inclination of the corrugations, thepositioning, width, and thickness of the foils, and by perforating thestrips or foil, forming them from woven wires, replacing them in partwith felted fiber members and the like (while undesirable for sealingcomponents, increased porosity may be advantageous or even requisite forother applications of the invention).

Still another advantage of our invention flows from the availability ofa wide variety of metallic foils, making it possible to fabricatestructures having widely different physical characteristics. Forexample, many oxidation resistance metallic materials are available infoil form; from these can be fabricated structures for high temperatureapplication. Also available are a number of heat treated or heattreatable materials which can be used when maxiumum resiliency andcompliance is desired. Further, strips of two or more different types ofmaterials can be readily employed in the same component to optimize itfor a particular application.

The structures of the present invention are of course far superior tothose of felted or woven metal fibers because of the lower surface areasand comparably greater oxidation resistance due to the use of stripsrather than fibers. For example, felted metal Hastelloy X seals are notusable at temperatures above 1200° F. Hastelloy sealing components inaccord with the present invention can in contrast be used attemperatures up to 1800° F.

Yet another advantage of the invention is a result of the edgewiserelationship of the foils to the support or backing member. Because ofthis relationship and the configurations of the interstices, the area tobe joined between the strips and the backing member is minimized with aconcurrent reduction in fabrication problems. At the same time the riskof distorting the component in the process of bonding the support orbacking member to the foil is significantly reduced.

A further important advantage of our novel structures is that they canbe made from materials which are difficult to form and to fabricate suchas TD NiCr, Haynes 188, Fe-Al and Ni-Al alloys, and titanium. Similarly,perforated, notched, and other opened foils which can otherwise behandled only with difficulty and at high cost can be readily fabricatedinto structures embodying the principles of the present invention.

At the same time our novel structures can, in contrast to those of thehoneycomb and comparable types, readily be fabricated in a variety ofshapes such as flat, joggled or stepped, cylindrical (straight, tapered,etc.), oblate, conical, hourglass, convergent-divergent, and others.

Another important advantage of the same general character is that ournovel materials can be reaily shaped and/or formed to precise dimensionsafter fabrication by any one or a combination of a variety of techniquessuch as bending, rolling, sizing, coining, deep drawing, bulging,swaging, stretch forming, shear spinning, grinding, lapping, and thelike.

A related advantage of the invention is that our novel structures can beformed by the foregoing and other techniques into configurations havingvery small radii or of very small diameters without deleteriousanti-classic effects. This attribute makes them useful as shaft sealsand/or similar devices.

Yet another advantage of our invention is that in circumstances where abacking member is employed, a variety of techniques for attaching thebacking member can be utilized. These include, but are not by any meanslimited to, welding, brazing (conventional and vapor phase), diffusionbonding, and the use of appropriate adhesives.

Similarly, backings of different thicknesses and materials and ofperforate, bimetallic, and other character may be employed to best suitcomponents in accord with the present invention for various applicatons.By selecting an appropriate method for attaching the backing member itcan be made removable so that it or the porous structure can be removedand replaced as the replaceable component becomes unserviceable.

Still another advantage of the present invention is that structuresfabricated in accord with the principles thereof are useful over a widetemperature range which varies from cryogenic temperature regions to3000° Kelvin or higher. We are not aware of any other single type ofsealing material, for example, which even remotely possess this degreeof versatility.

Yet another and of course highly important advantage of our invention isthat structures having the various advantages described above arecomparatively inexpensive. This stems in part from the design of ournovel structures. In addition, the fact that the porous structure can bemade by a continuous and simple wrapping operation also contributes tolower cost as well as the elimination or minimization of machining andother finishing operations which are usually necessitated when precisionis required. Also, the weight to volume ratio of our novel structures islow. As a result, they generally require less material than honeycomb,felted metal, and other similar components.

As indicated previously, our novel metallic structures are furtheradvantageous in that they are useful for many purposes other than thosediscussed above. Examples of applications for which they areparticularly suited include insulation, sound attenuation, andreinforcement for other materials. They may also be fabricated as pistonrings, slide valve seals, cryogenic bearings, seals, and valve members;our structures may also be used for still other purposes includingscreens, catalyst supports, diffusers and transpiration type heatexchange elements.

From the foregoing, it will be apparent that the primary object of thepresent invention resides in the provision of novel, improved,lightweight metallic structures.

A related and also important object of the invention is the provision ofnovel, improved metallic structures which are effective seals and areespecially useful as rub rings for turbine and compressor sections andthe like.

Another related and also important object is the provision of novel,improved metallic structures which are useful in a variety ofapplications embracing a wide range of temperatures and physicalconfigurations and requiring a wide diversity of physicalcharacteristics.

Other important but more specific objects of the present inventionreside in the provision of novel, improved metallic structures orcomponents:

1. which are porous, lightweight, strong, durable, and stable, and whichcan, at the same time, be made to be soft and resilient.

2. which are capable of minimizing wear on components having movementrelative thereto in applications where they contact moving or movablecomponents.

3. which are less expensive to fabricate then materials heretoforeavailable for comparable applications.

4. to which backing or support members can be brazed or otherwiseattached without filling the interstices between the strips with thebraze or other metal employed in a liquid phase to produce the bond.

5. which can be fabricated in a variety of configurations and from avariety of materials capable of imparting a wide range ofcharacteristics to the finished component including configurations andmaterials which can otherwise be produced and handled, if at all, onlywith difficulty and at high cost.

6. in which components of a variety of different configurations can beemployed to impart a diversity of characteristics including a wide rangeof pore sizes and configurations and various degrees of resilience orcompliance and abradability to the finished structure.

7. in which the degree of bonding between the metallic strips can beregulated or substantially eliminated.

8. which, in conjunction with the preceding object, have unbondedworking surfaces.

9. which do not exhibit capillarity and are substantially free fromconvective gas current flows.

10. which, in conjunction with the preceding object, have a low densityand are therefore good insulation materials.

11. which are usable over a wide temperature range from cryongenictemperatures to 3000° Kelvin or higher.

12. which are highly resistant to oxidation, even at elevatedtemperatures at which oxidation normally occurs.

13. which are substantially anti-clastic.

14. which can be filled with an abradable or other material to enhance,alter or provide additional properties and yet are highly effective inretaining the filler material in place.

15. which, when fabricated into rub rings or other gas sealingstructures, are capable of substantially eliminating axial leakageand/or pumping.

16. which have a high degree of elasticity or resiliency or rubcompliance and are therefore capable of expanding and otherwise changingin configuration to compensate for changing temperature conditions,misalignment in cooperating components, etc.

17. which, when employed as sealing components, are generally moreefficient than the sealing materials heretofore available.

18. which can be fabricated in or formed by a variety of manufacturingprocesses to desired shapes and/or precise tolerances.

19. which can be formed into components having small diameters and radiiwithout adversely effecting the characteristics of the structure.

20. in which the foil or strip assemblage and/or backing member isreplaceable.

21. which can be surface treated and/or utilized in conjunction withsurface treated components to reduce sliding or rubbing friction.

22. which are composed of a matrix of metallic foils or strips and abacking or support member or substrate attached to the matrix.

23. in which, in conjunction with the preceding object, the backingmember can be attached by a variety of techniques including methodswhich will avoid any significant distortion of the component which wouldimpair its functional capabilities.

24. in which, in conjunction with the two preceding objects, a varietyof backings of different types can be employed to impart differentcharacteristics to the final structural configuration.

25. which have various combinations of the foregoing attributes.

Other objects and features and additional advantages of the inventionwill become apparent from the appended claims and from the ensuingdetailed description and discussion, taken in conjunction with theaccompanying drawing, in which:

FIG. 1 is a generally schematic and fragmentary section through aturbine equipped with a rub ring fabricated in accord with theprinciples of the present invention.

FIG. 2 is a photograph of the rub ring;

FIG. 3 is a photograph of the same kind of structural material as thatemployed in the rub ring taken from a different angle;

FIG. 4 is a close-up of the structural material;

FIG. 5 is a view showing how the foils employed in the structuralmaterial are corrugated and assembled;

FIGS. 6-13 are views similar to FIG. 5 of other embodiments of theinvention;

FIG. 14 is a photograph of yet another embodiment of the invention; and

FIG. 15 is a view similar to FIG. 5 of an embodiment of the invention inwhich the foils of the structural members are spaced apart by wovenmetallic strips.

As discussed above, one of the applications in which the novelstructural members of the present invention may be used to particularadvantage is as a rub ring in a gas turbine. Such a turbine is shown infragmentary form in FIG. 1 of the drawing and identified by referencecharacter 10.

Turning now to FIG. 1, turbine engine 10 will typically include acompressor section (not shown) from which compressed air flows into acombustion section or combustor 12 where fuel is mixed with thecompressed air and the fuel-air mixture ignited and burned. From thecombustion section, the hot, compressed air-combustion products mixtureflows through a nozzle section 14 into a turbine 16 which includes awheel consisting of a plurality of turbine blades or buckets 18 fastenedto a rotatably mounted shaft (not shown).

As the hot fluid impinges on the turbine buckets, it rotates the shaftof the turbine wheel, which is connected to the turbine enginecompressor and may also be connected to load equipment such as agenerator, propeller, or the like, and, in most cases, to auxiliaryequipment. Alternatively, the turbine may be employed only to drive thecompressor and auxiliary equipment and the hot exhaust gases directedthrough an appropriately configured nozzle section to increase theirvelocity energy and thereby produce forces capable of propelling anaircraft or other vehicle.

The energy available to do work decreases to the extent that the exhaustgases flow through the gap 19 between the tips of the turbine blades 18and the casing 20 which houses the wheel 16.

For the reasons discussed previously, it is impossible to provide a zeroclearance between the tips of turbine blades 18 and casing 20.Accordingly, to keep the hot gases discharged through nozzle 14 fromflowing through gap 19, an annular rub ring 22 (see also FIG. 2) isdisposed in the gap between the casing and turbine wheel.

Referring now to FIGS. 2-4, rub ring 22 includes a matrix 26 whichconsists of metal strips 28 disposed in side-by-side relationship withthe edges of the strips at the opposite, inner and outer sides of thematrix. The matrix is surrounded by an annular backing or support member30, which is typically fixed to the strips in matrix 26 as by brazing orby any of the other bonding techniques discussed above.

As best shown in FIGS. 2 and 4, there are interstices 31 betweenadjacent strips. The interstices are provided by corrugating strips 28and then assembling them in a manner such that the corrugations inadjacent strips will come into contact at intervals therealong to spacethe strips apart and form the interstices therebetween.

Any desired shape of corrugation may be employed as well as stripshaving combinations of different corrugation configurations, orcorrugated and uncorrugated strips may be alternated as long as thestrips are kept from nesting.

The specific corrugation arrangement employed in rub ring 22 is shown inmore detail in FIG. 5. Referring now to this Figure, the corrugations 32in strips 28 extend at an angle across the strips and from edge-to-edgethereof. The strips are assembled so that the corrugations 32 inadjacent strips are inclined in opposite directions. Thus thecorrugations in the adjacent strips intersect in X-like patterns andspace apart the adjacent strips to form the interstices 31 therebetween.

As shown in FIG. 5, none of the interstices 31 extend completely throughmatrix 26. Consequently, the bonding material by which backing orsupport member 30 is attached is confined to those edge portions of thestrips nearest the support member, leaving the strips otherwise free tomove relative to each other.

This provides maximum rub compliance between the strips and the tips ofturbine buckets 18, permitting the edge of strips 28 facing wheel 16 toindependently and elastically yield or deform to a virtual zerotolerance fit with the turbine blades as the wheel rotates.

The foil edges in the matrix are preferably oriented in the samedirection as that in which wheel 16 rotates. Such orientation alsoincreases the rub compliance of the sealing structure.

To further increase the rub compliance the corrugations, if of inclinedcharacter, are preferably oriented so that the corrugations are inclinedin the direction of movement of the relatively movable components suchas the turbine buckets 18.

The matrix of rub ring 22 may be made in any desired manner. Forexample, the foils 28 can be wound in side-by-side relationship on arotating cylindrical mandrel. The facing or support member 30 is thenbonded to the exposed side 34 of the matrix and the mandrel removed tocomplete the manufacturing process.

The dimensions of the strips will be varied, depending upon the use towhich the structural member is to be put as will the diameters of theinterstices 31, the thickness of the facing 30, the materials from whichthe facing and strips are formed, etc. Typically, however, the distancebetween the two edges 34 and 36 of the matrix will range from 0.05 to1.00 inch; and the interstices will range from 0.005 to 0.250 inch indiameter.

The strips will typically be formed of 0.0005 to 0.010 inch thick sheetmaterial and will be somewhat thicker if made from a knitted or wovenmaterial.

Both the strips 28 and the support member 30 can be made from a varietyof metals, depending upon the use to which the member is to be put. Forhigh temperature applications, these include Hastelloy X and oxidationresistant alloys of the iron-chromium-aluminum andcobalt-chromium-aluminum-yttrium types.

If maximum elasticity is of importance, heat treatable alloys such asthe aluminum based 7075, 7178, and 2024 alloys; beryllium copper andberyllium nickel alloys; nickel and iron-based alloys such asInconel-X750, 718, and A-286; and titanium-aluminum-vanadium alloys canbe utilized.

Other exemplary metals from which the strips can be made include silverand tungsten and their alloys.

The strips can also be molded from refractories such as alumina andthoria which can be filled with fibers or other reinforcements ifdesired.

Still other variations which may be employed are to make the strips ofbimetallic or composite metallic-metallic or metallic-non-metallicmaterials. They may also be coated to change their characteristics.

The cell size will also depend upon the application or use of thestructural member. In sealing applications such as that illustrated inFIG. 1, the interstices can readily be made small enough that theturbine blades will "see" the matrix of the seal as a solid surface. Inthis circumstance, there will be essentially no leakage of gases pastthe tips of the turbine blades.

Again, depending upon the particular characteristics wanted in thestructural member, the interstices 31 between strips 28 may be leftunfilled. Or they may be filled with a variety of abradable materials(for example, Teflon, polyimides, graphites, boron nitrides, ceramics,metals, and various combinations of the foregoing).

The backing or support member employed in the structures we haveinvented can also vary considerably in character. Although it canobviously be of any thickness, the support member will typically, thoughnot necessarily, be from 0.0002 to 0.010 inch thick. It can be smoothand imperforate as shown in FIG. 2, or it can be embossed, perforated,expanded, or other material depending upon the application of theinvention. It can also be made from a wide variety of materials as justdiscussed, depending upon the intended use of the structure.

The support member can, in some applications, be omitted altogether. Inthis case the strips will be bonded together at one side of the matrixto keep the strips in the proper relationship.

It is to be remembered that the annular configuration of rub ring 22 isbut one of the many shapes which the structural members of the presentinvention may have. Other examplary shapes and techniques by which theycan be made were identified above.

Also, the member can be treated after it is assembled to alter itscharacteristics if the intended application so dictates. For example, itmay be desirable to minimize the tendency of the member to gall and/orto reduce its coefficient of friction.

Examples of post-fabrication treatments include nitriding, coating, etc.

Returning now to the drawing, FIGS. 6-14 illustrate other typicalstructural members in accord with the principles of the presentinvention. Structurally, these members differ from rub ring 22 primarilyin the manner in which the strips of the structural member matrix arecorrugated.

Thus the matrix 39 of the structural member 40 shown in FIG. 6 (whichalso includes substrate or support member 41) consists of strips 42 withinclined corrugations 44 alternated with foils 46 in which thecorrugations 48 extend normally across the strip. This arrangement isalso anti-nesting, and it provides interstices 50 between adjacentstrips.

In the matrix 51 of the structural member 52 shown in FIG. 7, strips 54with inclined corrugations 56 are alternated with foils or strips 58which also have inclined corrugations, 60. In this matrix, corrugations60 extend in the same direction as corrugations 56. However,corrugations 60 are less steeply inclined than corrugations 56, againproviding a strip assemblage which is anti-nesting and which providesinterstices 62 between the strips.

Still yet another exemplary structural member 64 is shown in FIG. 8. Inthe matrix 65 of this member, strips 66 having chevron shapedconfigurations 68 are alternated with strips 70 having inclinedcorrugations 72. This anti-nesting arrangement provides interstices 74between adjacent strips.

In the matrix 80 of the structural member 81 illustrated in FIG. 9, thestrips or foils 82 have arcuate or curved corrugations 84. The stripsare assembled so that the corrugations 84 of adjacent foils face in theopposite direction. This, again, keeps adjacent foils from nesting andprovides interstices 86 between the foils.

FIG. 10 depicts a structural member 90 in accordance with the principlesof the present invention, which is particularly useful in rub ring andsimilar applications. This structural member includes a matrix 92 ofmetallic strips 94. At one side 96 of the matrix, the strips are bondedto a support or backing member 98 of the type previously described.

Each of the strips 94 in matrix 92 has corrugations which are inclinedat the side of the matrix to which the backing strip 98 is attached. Thecorrugations also have a portion 104 extending normally across thestrips from the associated inclined portion 105 to the opposite side 106of the matrix.

Alternate strips 94 are assembled with the inclined portions 105 of thecorrugations facing in opposite directions. As in the precedingexemplary embodiments of the invention, this produces a non-nestingstructure with interstices 107 between the strips.

The structural member 108 of FIG. 11 is similar to structural member 90except that each of the strips 110 in the matrix 112 to which backingmember 114 is attached has corrugations 115 in which two end portions116 and 118 on opposite sides of a normally extending portion 120 facein opposite directions to provide a non-nesting arrangement withinterstices 122 between the strips.

The matrix 126 of the structural member 127 shown in FIG. 12 againillustrates how strips of two different types can be employed in thesame matrix. In matrix 126 strips 128 with chevron shaped corrugations129 are alternated with strips 130 having corrugations 132 extendingnormally across the strips, producing a non-nesting arrangement withinterstices 133.

In one structural member employing a matrix of the type illustrated inFIG. 12, the distance between the two sides 134 and 136 of the matrixwas 0.10 inch nominal. There were 40 corrugations per inch in strips 130and 20 corrugations per inch in the chevron corrugated strips 128.

As indicated previously, the foils or strips employed in the structuralmembers of the present invention may be made from knitted and/or wovenmetallic tapes and the like. FIG. 13 illustrates a structural member ofthis character.

More specifically, the structural member 140 illustrated in FIG. 13includes a matrix 142 of corrugated tapes 144 to which support member146 is attached. Tapes 144 were woven from strands of Inconel 600 andthen deformed into a generally sinusoidal configuration, providingcorrugations extending normally across the strips.

As can be seen from FIG. 13, the strips are non-nesting as assembled;and there are interstices 148 between the strips.

As was pointed out previously, the properties of structural members inaccord with the present invention can also be altered by perforating thefoils from which the structural member is made. A typical example of aperforated foil is shown in FIG. 14 and identified by referencecharacter 152. Foil 152 is substantially identical to the foil 46illustrated in FIG. 6 and described above except that perforations 154are formed in the foil at intervals therealong.

A structural member employing foils as illustrated in FIG. 14 would belighter and would tend to have greater rub compliance than thestructural member depicted in FIG. 6.

Other strips of a perforated, slotted or otherwise "opened" charactermade by notching the strips, fabricating them from expanded metal, etc.,would, of course, further alter and/or change these characteristics ofthe structural member.

We also pointed out previously that the interstices between the stripscan be formed by alternating appropriate spacers with the strips insteadof or in addition to corrugating the strips. A member 160 of thischaracter is illustrated in FIG. 15. The matrix 162 of the member ismade of un-corrugated foils 163 alternated with woven strips 164 whichspace foils 163 apart and devide the spaces therebetween into cells of asize determined by the thickness of the strands from which the stripsare woven, the tightness of the weave, etc.

The structural member 160 of FIG. 15 also includes two support members166 and 168, one being fixed to each side of matrix 162. As mentionedabove, this is another variation which can be employed to advantage incertain applications of the invention.

It will be apparent from the foregoing that there are countless forms ofmetallic foils or strips and combinations thereof which can be employedin the practice of the present invention. It is to be understood,therefore, that the embodiments of the invention hereinbefore describedare intended to be merely illustrative only and not inclusive, inasmuchas many alternate arrangements which will prevent nesting and provideinterstices between the strips can be employed.

From the foregoing illustrations of various embodiments of the presentinvention, it will be apparent that the invention may be embodied inother specific forms without departing from the spirit or essentialcharacteristics thereof. The present embodiments are therefore to beconsidered in all respects as illustrative and not restrictive, thescope of the invention being indicated by the appended claims ratherthan by the foregoing description; and all changes which come within themeaning and range of equivalency of the claims are therefore intended tobe embraced therein.

What is claimed and desired to be secured by Letters Patent is:
 1. In amachine having two, juxtaposed, relatively movable components, meansproviding a seal between said components comprising an assemblage ofdeformable metallic strips disposed in side-by-side relationship withthe opposite edges of the strips respectively facing one and the otherof said components; means spacing said strips apart to provideinterstices therebetween; and a backing member disposed between saidassemblage of metallic strips and one of said components for maintainingsaid strips of the assemblage in the aforesaid relationship; the edgesof the strips facing said one of said components being fixed to thebacking member and the edges of the strips facing the other of saidcomponents being free of attachment to each other, whereby the portionsof the strips nearer to said other component can move relative to eachother and to said other component to provide a compliant seal betweensaid assemblage of metallic strips and said other component; the meansspacing said strips apart comprising corrugations formed in at leastpart of said strips; and said strips being oriented to extend in thedirection of relative movement between said components with thecorrugations at the edges of the strips which are free of attachment toeach other being at an angle of less than 90° to said direction ofmovement to thereby minimize the resistance to deformation offered bysaid strips.
 2. The machine of claim 1 wherein all of said strips arecorrugated with the corrugations extending diagonally from edge-to-edgeof each said strip, the corrugations in alternate strips extending inopposite directions whereby the corrugations in adjacent strips comeinto contact to space apart and provide the interstices therbetween. 3.The machine of claim 1 wherein all of said strips are corrugated withthe corrugations extending diagonally from edge-to-edge of each strip,the corrugations in all of said strips extending in the same directionand the corrugations in adjacent strips being inclined at differentangles relative to the edges of the strips, whereby the corrugations inadjacent strips come into contact to space the strips apart and providethe interstices therebetween.
 4. The machine of claim 1 wherein thecorrugations in at least alternate strips are V-shaped, saidcorrugations spacing said strips apart and thereby providing theinterstices therebetween.
 5. The machine of claim 1 wherein onlyalternative ones of said strips are corrugated.
 6. The machine of claim1 wherein the corrugations in the strips are of at least two differentconfigurations.
 7. The machine of claim 1, wherein the corrugations inadjacent strips are in a mirror image relationship relative to thecorrugations in the strips thereadjacent.
 8. The machine of claim 1wherein the corrugations in said strips have an arcuate configuration.9. The machine of claim 8 wherein the corrugations in adjacent stripsface in opposite directions.
 10. The machine of claim 1 wherein thestrips of the seal providing means are composed of at least twodifferent metallic materials.
 11. The machine of claim 1 wherein atleast part of the strips of the seal providing means are of knitted orwoven metallic fibers.
 12. The machine of claim 1 wherein at least partof the strips in the assemblage are of perforated, notched, or otheropen construction.
 13. The machine of claim 1, wherein there is afriction reducing coating on the surface of said other component whichis contacted by the seal providing means and/or on those edges of thestrips contacted by said other component.
 14. The machine of claim 1,wherein at least part of said strips are of woven or felted strandconstruction.
 15. In a machine having two, juxtaposed, relativelymovable components, means providing a seal between said componentscomprising an assemblage of deformable metallic strips disposed inside-by-side relationship with the opposite edges of the stripsrespectively facing one and the other of said components; means spacingsaid strips apart to provide interstices therebetween; and backing meansdisposed between said assemblage of metallic strips and one of saidcomponents for maintaining said strips of the assemblage in theaforesaid relationship; the edges of the strips facing said one of saidcomponents being united with the backing means and the edges of thestrips facing the other of said components being free of attachment toeach other, whereby the portions of the strips nearer said othercomponents can move relative to each other and to said other componentand provide a compliant seal between said assemblage of metallic stripsand said other component; there being corrugations formed in at leastpart of said strips; and said strips being oriented to extend in adirection of relative movement between said components with thecorrugations at the edges of the strips which are free of attachment toeach other being oriented at an angle of less than 90° with respect tosaid direction of relative movement.
 16. In a machine having two,juxtaposed, relatively moveable components, means providing a sealbetween said components comprising an assemblage of deformable metallicstrips disposed in side-by-side relationship with the opposite edges ofthe strips respectively facing one and the other of said components;means spacing said strips apart to provide interstices therebetween;means for maintaining said strips of the assemblage in the aforesaidrelationship; the edges of the strips facing said one of said componentsbeing united with said last mentioned means and the edges of the stripsfacing the other of said components being free of attachment to eachother, whereby the portions of the strips nearer said other componentcan move relative to each other and to said other component and providea compliant seal between said assemblage of metallic strips and saidother component; there being corrugations formed in at least part ofsaid strips; and said strips being oriented to extend in a direction ofrelative movement between said components with the corrugations at theedges of the strips which are free of attachment to each other beingoriented at an angle of less than 90° with respect to said direction ofrelative movement. .Iadd.
 17. In an abradable fluid seal for use in thespace between two relatively movable members, such as the circular spacebetween the cylindrical path of the rotating blade tips in an aircraftgas turbine and the surrounding bore wall of the stationary casing ofthe turbine wherein the seal has a circular length, an axial dimensionand a radial dimension, an improvement comprising:A. A thin elongatefluid-seal strip having opposite inner and outer edges, a narrow widththerebetween, an outer base portion extending lenghtwise along saidouter edge and widthwise partially across the width of the strip, aninner seal portion extending lengthwise along said inner edge andpartially across the width of the strip, and, over a given length, onesuccession of undulations in its outer base portion and anothersuccession of corresponding undulations in its inner seal portion,1. thecrests, of its base portion undulations, extend across the width of saidbase portion, and
 2. the crests, of its seal portion undulations, extendacross the width of said seal portion. .Iaddend.